What endotoxin is
Endotoxin is lipopolysaccharide (LPS), a structural component of the outer membrane of Gram-negative bacteria. It is released when bacteria multiply and, in large quantities, when they are killed — including by antibiotics.
LPS is recognised by the innate immune system through Toll-like receptor 4 on monocytes, macrophages and endothelial cells. That recognition is normally protective; at high circulating load it becomes the initiating event of a systemic inflammatory cascade.
From trigger to shock
TLR4 activation drives transcription of pro-inflammatory cytokines including TNF-alpha, IL-1 and IL-6. These mediators cause vasodilation, increased capillary permeability, microvascular thrombosis and myocardial depression.
Clinically this presents as hypotension unresponsive to fluid, rising lactate, escalating vasopressor requirement and progressive organ dysfunction. The cascade is self-amplifying, which is why late intervention tends to be less effective than early intervention.
Why endotoxin load is measured
Endotoxin activity assays allow the endotoxin contribution to a patient's shock state to be estimated, which helps distinguish patients in whom endotoxin removal is a rational target from those whose deterioration is driven by other mechanisms.
This matters because adjunctive purification therapies are resource-intensive and time-critical: identifying the patients most likely to respond is part of using them well.
Implications for treatment
Source control and antimicrobials remain the foundation of care. Where endotoxin and cytokine load appear to be sustaining the shock state, removing them extracorporeally is used as an adjunct, alongside — not instead of — standard sepsis bundles.
This article is general educational information for healthcare professionals and is not clinical advice or a treatment recommendation. Always refer to the current instructions for use and local clinical guidance.